1. Field of the Invention
This invention relates to a canister for use in a breathing apparatus which is used in water or on land, and particularly to a canister for a semi-closed type of breathing apparatus in which carbon dioxide is removed from breathing air circulating in a breathing circuit and breathing air is supplied from an air tank into the breathing circuit.
2. Description of Related Art
In general, a semi-closed type of breathing apparatus is equipped with a breathing bag, a valve unit, a canister (carbon dioxide absorber) for absorbing carbon dioxide and an air tank. In the semi-closed type of breathing apparatus thus constructed, carbon dioxide is removed from breathing air (gas) circulating in the breathing circuit in the canister, and the breathing air is supplied from the air tank into the breathing circuit while surplus breathing air is discharged from the breathing bag.
This type of conventional breathing apparatus is disclosed in Japanese Laid-open Patent Application No. 50-108797 and Japanese Laid-open Utility Model Registration Application No. 54-3000. The canister of the breathing apparatus as disclosed in these applications is designed in a cylindrical shape. The upper bottom of the canister is equipped with a connection port which is connected to an exhaling duct, and the lower bottom thereof is equipped with a connection port which is connected to an inhaling duct. In this conventional canister, the breathing air flows from the upper bottom to the lower bottom in the canister.
However, in the conventional semi-closed type of breathing apparatus having a canister as described above, when the canister is used while integrally combined with an air tank, a breathing bag and a float adjusting device (buoyancy vest), there occurs a problem that the assembly between the canister and the other elements such as the air tank, the breathing bag, etc. cannot be smoothly performed because of the cylindrical shape of the canister.
On the other hand, when the canister is designed in a square or rectangular shape, the breathing air flow is reduced at the corners, and thus there occurs a problem that a uniform flow of the breathing air cannot be obtained.